US8842403B2 - Electric system - Google Patents

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US8842403B2
US8842403B2 US13/058,731 US200913058731A US8842403B2 US 8842403 B2 US8842403 B2 US 8842403B2 US 200913058731 A US200913058731 A US 200913058731A US 8842403 B2 US8842403 B2 US 8842403B2
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limit value
measured current
value
monitoring time
load
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US20110141643A1 (en
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Alwin Hummel
Harald Schweigert
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Siemens AG
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Siemens AG
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/04—Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of DC component by short circuits in AC networks
    • H02H1/043—Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of DC component by short circuits in AC networks to inrush currents
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/006—Calibration or setting of parameters

Definitions

  • the invention relates to automated systems which include a supply circuit having hardwired loads and, more particularly, to an electrical system having at least one current-consuming load that is protected by a protective device, where a tripping parameter, i.e., a tripping current, of the protective device can be set.
  • a tripping parameter i.e., a tripping current
  • the invention also relates to a method for operating the electrical system.
  • automation systems are production systems, process engineering systems or other industrially or commercially usable large-scale installations. Due to different requirements, systems of this kind are very rarely implemented in an identical design. Consequently, each system comprises different numbers and different sizes of loads. In order to avoid the outage of an entire system and, consequently, for example, interruptions to production in the event of a fault in a single load, each of the loads must be protected by a protective device, such as a cutout or circuit breaker.
  • a plurality of electrical loads of a system are combined into groups, with each group being protected against overloads or short-circuit by a protective device.
  • the groups are chosen such that the shutdown of one group does not inevitably lead to the total outage of the entire system.
  • the protection for the loads or load groups is usually specified by a project engineer and subsequently installed or set by a technician.
  • adjustable protective devices are mainly used in these situations so as to allow adjustments to the tripping current to be performed as late as during an initial startup phase. The reason for this resides in the fact that the actual current consumption of the loads or load groups can only be determined to an inadequate degree during the project engineering and configuration phase.
  • too highly dimensioned protective devices in contrast, generally go unnoticed because not every operating state of every individual load or every individual load group can be taken into consideration, and because of the actual current consumption is measured during an initial startup. Selective tripping of individual protective devices is no longer ensured because in the event of a short-circuit or an overload it is sometimes no longer the too highly dimensioned, protective device disposed directly upstream of the affected load which trips, but a pre-fuse. As a result, major parts of the system are disconnected from power unnecessarily. In the worst case, the capacity of a power source (e.g., 24V control voltage) can be exceeded due to the short-circuit current, resulting in a failure of the entire system.
  • a power source e.g., 24V control voltage
  • an electrical system and method for operating the electrical system that includes a control unit to which a measured current value of the current consumed by the at least one load is supplied, where the control unit generates a new limit value as a function of the previous characteristic curve of the measured current value and the limit value is specified to the protective device for the purpose of setting a tripping parameter.
  • the control unit permits ongoing adjustment of the tripping parameters, i.e., the tripping current, according to the actual operating conditions. Cyclic current peaks are detected and, with a safety margin factored in, form the benchmark for specifying the limit value adjusted at time intervals for automatic corrective adjustment of the tripping parameters.
  • a protective device an isolating fuse or an electronic cutout is provided which limits the current to a predefined value in the event of a fault.
  • An excessively high disconnect value of the protective device that is not detected during the initial startup phase is corrected during operation of the system through specification of the adjusted limit value.
  • the limit value is derived directly from the characteristic curve of the actually occurring current consumption of the corresponding load. In this way, it is ensured that the tripping conditions of the protective device are matched to the given conditions at all times.
  • the at least one load is supplied by a regulated clocked power supply.
  • Power supplies of this kind typically have a current limiting device just above the rated current. For this reason, it is particularly important that the protective device provided for selective disconnection of an affected load is not overdimensioned. In other words, it must be ensured that an adequate short-circuit capacity is present for tripping the protective device. With a too highly dimensioned protective device, the clocked power supply would regulate the output voltage downward without the protective device separating the defective load from the rest of the supply network of a system.
  • Adjusting the tripping current of the protective device according to the actual current consumption of a load connected to the power supply ensures that, in the event of an overload as a result of a fault, the load will be disconnected by tripping of the protective device.
  • This is particularly advantageous when a plurality of loads are connected to the same power supply. In that case, each load is protected for example, by its own dedicated protective device, so that a defective load does not result in all the connected loads being disconnected. This therefore avoids a situation in which the power supply is regulated downward, and as a result the supply voltage drops before the protective device of a defective load is tripped.
  • those electric circuits can be disconnected whose current flow at the present time is above the historic average value.
  • the current which results as the average value of the most recent monitoring time interval (e.g., 1 day) or as a percentage of the set limit value, for example, should be regarded as the historic average value. If the power supply were to be overloaded, the entire system would go down. It is therefore expedient to deactivate all circuits which could be responsible for excess consumption.
  • control unit includes a first memory which, when triggered by a timer, stores measured current values of the load. In this way, a history of the measured current values is available for specifying the new limit value for the tripping current of the protective device.
  • control unit includes a microcontroller which, at predefined time intervals, generates a limit value from the measured current values stored in the first memory, where the limit value is stored in a second memory and supplied to the protective device. Provision for determining suitable limit values for every operating situation is made by an easy-to-program microcontroller. Different methods for specifying a limit value for the tripping current can therefore be used according to requirements.
  • the limit value stored in the second memory up to the next time the limit value is determined represents the control variable for adjusting the tripping conditions of the protective device connected to the control unit.
  • the protective device is implemented as a controlled electronic protective device.
  • the control unit for specifying the limit value can be integrated into the controller of the electronic protective device.
  • the electrical system in accordance with the invention is operated by a method in which after a monitoring time interval has elapsed the maximum measured current value that occurred within the monitoring time interval is determined, and the maximum measured current value is used together with at least one stored maximum measured current value of a preceding monitoring time interval or a predefined start value (e.g., the rated current) at the initial startup of the system to determine therefrom the limit value for setting the tripping current.
  • the control unit specifies the new tripping current of the protective device only after a monitoring time interval which corresponds to an executed operating cycle having a detected current consumption peak.
  • the control unit is supplied with a feed voltage of the at least one load and that the limit value is determined as a function of the level of the feed voltage such that a static limit value is specified during ongoing operation and that a higher dynamic limit value is specified during a switch-on operation of the at least one load.
  • a static limit value is specified for ongoing operation, where the static limit value typically is lower than the inrush current of the load.
  • a dynamic limit value is specified for the protective device, where the dynamic limit value takes into account the inrush current of the load. This is particularly important for loads with high inrush currents.
  • the static limit value were to be higher than the inrush current, a fault current of the load during ongoing operation could go undetected.
  • the measured current value is beneficially filtered prior to being stored so that insignificant current peaks and sources of interference are masked out during the determination of a maximum measured current value.
  • the filter thus prevents the limit value determination process from reacting to sources of interference and extremely short load peaks that can be triggered by switching actions for example. During the short load peaks an electronic cutout would switch into the linear or current limiting mode and build up dissipation loss.
  • an adjustable duration of the monitoring time interval is specified to the control unit. This is beneficial especially when known operating cycles of the electrical system are present.
  • the duration of the monitoring time interval is then made equal to the cycle duration, for example, or set to a longer time than the cycle duration.
  • the duration of a monitoring time interval is defined such that the characteristic curve of the measured current values is initially recorded for the purpose of detecting a recurring sequence of consumption peaks and consumption minima, and such that following on therefrom a monitoring time interval is defined such that one consumption peak and one consumption minimum each fall within one monitoring time interval.
  • the duration of a monitoring time interval is determined by the occurrence of a predefinable number of instances of a specific threshold value of the measured current value and/or of a current-time integral being exceeded. Such an approach is useful, for example, for systems whose loads have irregular operating times. Succeeding monitoring time intervals then last different lengths of time depending on how often a current threshold value or a threshold value of the current-time integral is reached.
  • a safety margin is advantageously applied to the maximum measured current values determined in the monitoring time intervals. There is then an upward safety margin for the next monitoring time interval, such that a normal increase in current consumption (e.g., due to weather conditions) does not lead to tripping of the protective device.
  • This safety margin can range between 1% and 50% for example.
  • the safety margin is increased or reduced according to a predefinable curve with increasing operating time of the electrical system. In this way, as the duration of the current consumption monitoring increases, the set tripping current is brought closer to the actual conditions.
  • the limit value is specified as an average of the maximum measured current values determined within elapsed monitoring time intervals and those to which the safety margin has been applied.
  • the maximum measured current value determined in the most recently elapsed monitoring time interval and the still applicable limit value are averaged to determine a new limit value.
  • recourse can also be made to a plurality of historic limit values for averaging purposes, thereby achieving a stronger weighting of the preceding maximum measured current values.
  • the maximum measured current value of the most recently elapsed monitoring time interval is weighted more strongly than the values of the previously elapsed monitoring time intervals. In this way, it is ensured that ongoing changes in the operation of the system lead to a corresponding change in the tripping conditions of the protective device.
  • a further possibility consists in changing the weighting as the number of elapsed monitoring time intervals increases. This enables a slower or faster approximation to the current situation to be achieved.
  • the power consumption increases slowly as a result of contaminating fans, poor lubrication or seasonal stiffness of actuating elements.
  • a fault current needing to be switched off on the other hand, what occurs in the majority of cases is a pronounced current peak or an overcurrent which increases to a maximum value in a very short rise time and remains there.
  • a dynamic limit value is defined such that during permissible overcurrents the characteristic curve of the measured current value is recorded and that a characteristic curve for the dynamic limit value is specified as a function of a plurality of such characteristic curves.
  • Permissible overcurrents occur, for example, when loads are activated or when capacitors are charged during a switch-on operation. Accordingly, an envelope which is produced as a result of overlaying a plurality of permissible overcurrent characteristic curves, with inclusion of a safety margin, is specified as a tripping condition for the protective device.
  • the permissibility of an overcurrent is generally determined by the duration of the occurring overcurrent and its magnitude in relation to a rated current.
  • a current-time integral which is derived from a plurality of characteristic curves of the measured current value during a switch-on operation, is specified as the dynamic limit value.
  • the tripping criterion for the protective device is then likewise determined by a current-time integral of an occurring overcurrent.
  • the limit value and/or the characteristic curve of the limit value are/is limited by an upper limit which is predefined by the fire protection conditions applicable to the components which are disposed downstream of the protective device and/or by their capacity.
  • an upper limit which is predefined by the fire protection conditions applicable to the components which are disposed downstream of the protective device and/or by their capacity.
  • a maximum value or a specific time characteristic curve is predefined as the limit value.
  • a critical value is predefined for the increase in a limit value and, an alarm signal is triggered upon the critical value being exceeded.
  • the overheating of a bearing for example, can be detected before a total failure occurs or before the tripping conditions of the corresponding protective device are reached. It should be left to the user to choose only an increase over a year to mask out atmospheric conditions, or some other time period.
  • control unit is supplied with an external signal by which the duration of the monitoring time intervals is modified by a predefinable factor on an event-related basis. Shorter monitoring time intervals than during ongoing operation can be specified after a system shutdown or replacement of a defective protective device. The tripping current is then adjusted more rapidly to the prevailing operating conditions based on a preset starting value.
  • control unit is supplied with a reset signal by which a limit value is reset to a default value.
  • a reset signal by which a limit value is reset to a default value. This is useful after interruptions in the operation of the electrical system to execute a full operating cycle with the default value before a new limit value is specified to the protective device.
  • the default value specifies to the protective device a breaking current defined by the fire protection provisions applicable to the downstream circuit elements.
  • the reset signal can also be present at the control unit for a longer period of time, thereby inhibiting the forming of a new limit value for the duration of said time period. This is useful, such as for fault localization in the case of different switching actions of individual loads.
  • This default value is also specified to the protective device at the time of an initial startup of the electrical system. In this way, it is ensured that from the outset the maximum values of the current or of the current-time integral predefined for the current-carrying elements of the system by the fire protection provisions are not exceeded.
  • the present limit value or, as the case may be, the static and/or dynamic limit value as well as the present measured current value and/or the characteristic curve of the measured current value are/is indicated by a suitable display unit and/or output over an interface.
  • the limit values of the most recent monitoring time intervals e.g., 64 daily limit values
  • the measured current values of the last milliseconds which are stored, e.g., in a ring buffer can be read out. In this way the present state of the electrical system is evident at all times to operating personnel of the system.
  • FIG. 1 shows an arrangement with adjustable protective device in accordance with the invention
  • FIG. 2 shows an arrangement with a current-limiting protective device in accordance with the invention
  • FIG. 3 shows an arrangement with an exemplary schematic block diagram of the control unit in accordance with the invention
  • FIG. 4 shows an arrangement with a breaking protective device in accordance with the invention
  • FIG. 5 shows an arrangement with a plurality of mechanical circuit breakers connected in parallel in accordance with the invention
  • FIG. 6 shows graphical plots of curve shapes under dynamic loading
  • FIG. 7 shows a graphical plot of the maximum measured current values and limit values derived therefrom over time
  • FIG. 8 is a flow chart of the method in accordance with the invention.
  • FIG. 9 is a flow chart of the method including early fault detection in accordance with the invention.
  • FIG. 1 shows an embodiment in accordance with the invention.
  • a load 4 is connected to a feed voltage U in , such as an alternating-current voltage of a power supply network.
  • the feed voltage U in can, however, also be an output direct-current voltage of a switched-mode power supply.
  • a protective device S is disposed in the power path. In the simplest case the device consists of a mechanical switch which is controlled by a control unit 1 .
  • the tripping of the protective device S occurs based on predefined tripping conditions, where the corresponding tripping parameters are settable by the control unit 1 .
  • Suitable tripping parameters include a value for the tripping current, a maximum permissible duration of an overcurrent or a maximum permissible line temperature.
  • a disconnection or current limiting of the downstream load 4 is then performed if one of the tripping parameters is exceeded.
  • At least one tripping parameter of the protective device S is set to a new value after a monitoring time interval has elapsed.
  • the current consumed by the load 4 is measured by a current measuring device 3 and supplied as a measured current value to the control unit 1 .
  • the control unit 1 includes suitable a storage device for forming a history which initially serves for determining a maximum value during an elapsed monitoring time interval.
  • a maximum measured current value is therefore determined and stored for each monitoring time interval to form a limit value therefrom for adjusting a tripping parameter.
  • the average of at least two most recently determined maximum measured current values is used as the limit value.
  • a safety margin should also be provided.
  • a default value e.g., a rated current
  • I action(n+1) [( Î (n)+ Î (n ⁇ 1) ]/2
  • I action(n+1) [( Î (n) +Î (n ⁇ 1) *X ]/(1+ X )
  • the thus determined limit value is specified to the protective device as the new tripping current either directly or according to a scale. For example, if the change in the tripping current of a protective device is possible only in increments of ten, then the value that is next above the determined limit value is specified as the tripping current.
  • the correct setting of a tripping parameter is dependent on the duration of the monitoring time intervals.
  • the choice of the monitoring time intervals is geared to the operating cycles of the electrical system.
  • an operating cycle is determined by a pattern in the sequence of different operating states of the system component that is disposed downstream of the protective device, where the pattern occurs repeatedly in similar form in each operating cycle.
  • Such a system component can include either only one variably operated load or a plurality of loads operated in time-staggered fashion.
  • the pattern in the sequence of different operating states is produced, for example, as a result of recurring method steps or as a result of a predefined shift operation of a production system.
  • the advantage of the present invention takes effect in this case when the time characteristic of the current consumption of the loads protected by the protective device is not precisely predictable or the overhead required for the determination process is too high.
  • FIG. 2 shows an arrangement having a protective device S embodied as an electronic cutout.
  • a semiconductor switch disposed in the power path is driven in a pulsed or linear manner in the event of a fault, and in this way the current is held at a predefined maximum value irrespective of the behavior of the load, or the rated load prior to the occurrence of the fault situation (e.g., a short-circuit).
  • a mechanical or electromechanical cutout 5 e.g., a circuit breaker
  • FIG. 3 An exemplary embodiment of the control unit 1 is shown in FIG. 3 .
  • the load current is measured by a current measuring device 3 which includes a shunt resistance 6 by which the measured current value I actual is determined with a differential amplifier 7 .
  • the measured current value I actual is supplied, on the one hand, to a comparator 9 and, on the other hand, to a microcontroller 8 by an analog-digital converter 10 .
  • the comparator 9 compares the measured current value I actual with a reference value which is generated by the microcontroller 8 and passed on to the comparator 9 through a digital-analog converter 11 .
  • the output of the comparator 9 is connected, on the one hand, to the microcontroller 8 for determining a monitoring time interval and, on the other hand, to a gate drive 12 for driving the semiconductor switch of the protective device S in a pulsed or linear manner.
  • the control unit 1 embodied as a microcontroller receives the measured value of a current measuring device 3 from an analog-digital converter 10 . If the present tripping parameter is exceeded, a tripping signal is transmitted by the microcontroller through a signal amplifier 14 to the switching element of the protective device S. If a mechanical switching element is used, the defective load 4 is disconnected from the feed voltage U in .
  • An electronic switch can be used for limiting an overcurrent.
  • control unit 1 is supplied with a temperature value ⁇ which signals a critical line temperature and is measured by a temperature sensor 13 .
  • the temperature value ⁇ is used, for example, as a further tripping parameter or for determining the loading at the present instant in relation to the maximum permissible loading with regard to the fire protection regulations.
  • FIG. 5 A further possibility of limiting an overload current by the protective device S is shown in FIG. 5 .
  • a plurality of switches S 1 . . . Sn are connected in parallel in the power path.
  • the load current flows through a first switch S 1 .
  • a resistor R 1 . . . Rm is disposed in series with each of the remaining switches S 2 . . . Sn.
  • Each switch S 1 . . . Sn is controlled by the control unit 1 . If a load 4 is defective, the first switch S 1 is opened and one or more of the remaining switches are closed. In this arrangement the values of the resistors R 1 . . .
  • Rm are binary-stepped, for example, so that stable limiting of the overcurrent is effected through closing the corresponding switches S 2 . . . Sn. If the switches S 1 . . . S 2 are implemented as semiconductor elements, an additional fusible cutout 5 should be provided in the power path for fire protection reasons.
  • a protective device S is tripped as a result of a static or dynamic limit value of the tripping current being exceeded.
  • An exceeding of the dynamic limit value is identified by the characteristic curve of a transient overcurrent and is usually established by a current-time integral.
  • FIG. 6 shows graphical plots of various characteristic curves of the current during a switch-on operation.
  • the static limit value G stat determines the tripping current during ongoing operation.
  • the dynamic limit value G dyn is indicated as an envelope over tolerable characteristic curves M 1 , M 2 of an inrush current. At no time do the tolerable characteristic curves M 1 , M 2 exceed the characteristic curve of the dynamic limit value G dyn .
  • characteristic curve M 3 of an inrush current both the static limit value G stat is exceeded for a longer time than permitted and the current-time area of the dynamic limit value G dyn is also exceeded. Consequently, the protective device S is tripped.
  • the dynamic limit value G dyn is also adjusted to the actual operating conditions of the electrical system.
  • a default value which takes into account the maximum tolerable overvoltages at the time of the commissioning of the system, is initially specified to the protective device S.
  • the default value corresponds, e.g., to the maximum current limiting capacity of an electronic limiter or to the I 2 t value of a sensitive load.
  • the current consumption of the load 4 or of the load group is measured during a monitoring time interval and evaluated.
  • the feed voltage U in is additionally monitored by the control unit 1 , where a switch-on operation is detected by a drop in the feed voltage U in .
  • the static limit value G stat the tolerable overvoltages during a switch-on operation are masked out by a suitable filter (analog or digital). The interference peaks are accordingly ignored during the forming of the maximum measured current values of a monitoring time interval.
  • the dynamic limit value G dyn In order to adjust the dynamic limit value G dyn to the actual operating conditions, on the other hand, only the tolerable overcurrent characteristic curves are used.
  • characteristic curves of transient overcurrents are stored, for example, during one or more monitoring time intervals and an envelope is formed therefrom, in which case a safety margin should be provided.
  • the dynamic limit value G dyn determined in this way must not exceed the default setting, because this represents the limit for compliance with the fire protection requirements.
  • the characteristic curve of the load current is then either constantly compared with the envelope characteristic curve of the set dynamic limit value G dyn , or a current-time integral of the load current is constantly formed and compared with a dynamic limit value G dyn expressed as a current-time integral.
  • FIG. 7 An exemplary determination of a static limit value G stat is illustrated in FIG. 7 , where the load current I is plotted over the operating time t.
  • the operating cycles of the corresponding electrical system follow a fixed daily rhythm, i.e. the current consumption patterns are repeated in a similar manner every 24 hours. Accordingly, a monitoring time interval is set at 24 hours.
  • a default limit value G 0 is set initially.
  • the default limit value G 0 is maintained after startup until such time as an approximately repeating pattern of the load current characteristic curve is revealed from the recording of the measured current value.
  • maximum and minimum current values are particularly evaluated to derive operating cycles therefrom.
  • the monitoring time intervals for the further determination of the limit values are then set in accordance with these operating cycles. If no pattern for the current consumption can be recognized over a relatively long period of time, an adequate length of time (defined as a default value), such as one week, is set as the monitoring time interval for determining a new limit value.
  • the maximum measured current value that occurred during the monitoring time interval is determined and a safety margin Res is applied to the maximum measured current value.
  • the value formed in this way is specified to the protective device as the first adjusted limit value G 24 .
  • the limit value G 24 forms the tripping current of the protective device S.
  • the new maximum measured current value, to which a safety margin Res is in turn applied is determined from the recording of the load current in the second monitoring time interval after the monitoring time interval has elapsed.
  • the new limit value G 48 is then determined as the average value of the maximum measured current value to which the safety margin Res has been applied and the still valid limit value G 24 .
  • a weighting can be applied, for example, to make greater allowance for the most recently prevailing operating states.
  • the limit values G 72 , G 96 are formed in the same way after the succeeding two monitoring time intervals have elapsed. During the fifth monitoring time interval, the most recently determined limit value G 96 applies. Shortly before 120 h in FIG. 7 , a load current occurs that exceeds the limit value G 96 and leads to an activation of the protective device S.
  • a measured current value that leads to the tripping of the protective device S is masked out during the subsequent forming of a maximum measured current value of a monitoring time interval. Accordingly, after a fault that has occurred has been rectified and a system restart performed, the most recently valid limit value and the most recently determined maximum measured current value will be used for determining the next limit value without taking the fault current into account.
  • a default limit value can be specified to the protective device S following a restart and the determination of the succeeding limit values starts based on the default limit value.
  • FIG. 8 shows an exemplary signal scheme of the control unit 1 .
  • the load current I is measured by a current measuring device 3 .
  • Sources of interference and tolerable dynamic load peaks are masked out a filter and the thus filtered measured current signal I′ is supplied to an analog-digital converter A/D.
  • the time constant of the filter is aligned to the time that, e.g., an electronic cutout can run in the active current limiting mode (U*I at the power transistor of the cutout, such as 20-50 ms).
  • the ongoing filtered measured current values are stored in a maximum value memory SP(Î′) and are available to a microcontroller ⁇ C for the purpose of forming a maximum measured current value.
  • a timer CLOCK determines the duration of a monitoring time interval. The duration of the monitoring time interval can be adjusted by a corresponding signal transducer 1 d/10 sec.
  • the microcontroller ⁇ C calculates a new limit value from the present maximum measured current value and the still valid limit value. This is effected in the simplest manner by averaging. Limit values of past monitoring time intervals are stored in a history memory SP(G hist ) and are available to the microcontroller ⁇ C.
  • the newly calculated limit value is stored in an output memory SP(G) and forwarded to the controller STG of the protective device for the purpose of adjusting a tripping parameter.
  • the microcontroller ⁇ C is also supplied with the signal of a feed voltage monitoring element ÜW(U in ) for detecting a switch-on operation.
  • the dynamic inrush current of the connected load or load group is filtered out during the determination of the maximum measured current value.
  • a dynamic limit value is used as the tripping parameter of the protective device S during a switch-on operation.
  • the signal scheme depicted in FIG. 9 takes into account a slow current increase of a load which has a creeping fault.
  • the maximum value memory SP(Î′) is supplied, on the one hand, with the filtered measured current values and on the other hand, by the feed voltage monitoring element ÜW(U in ) with a signal for masking out inrush currents.
  • the measured current values and, on the other hand, the limit values of the elapsed monitoring time intervals are stored in a history memory SP(Hist).
  • An averager MW accesses the history memory SP(Hist) and calculates a new limit value from the stored values.
  • the history memory SP(Hist) is connected to a data reduction device Red for managing the stored values.
  • the values stored in the history memory SP(Hist) are supplied to an evaluation unit I/t for the purpose of determining the load-time behavior.
  • the time intervals within which high current consumption values are recorded are checked. On the basis of this evaluation, the monitoring time intervals can be adjusted by a corresponding signal transducer 1 d/10 sec (if, e.g., 24 h is not sufficient as an average time period).
  • the monitoring time interval can also be modified by operating personnel, optionally with the possibility of an automatic reset. This is useful, for example, for defining a learning period with short monitoring time intervals.
  • the new limit values formed are supplied to a detector DETECT for the purpose of detecting a slow increase in current.
  • a signal is output to a warning device which signals to the operating personnel that a creeping fault is present.
  • a dynamic limit value G dyn is specified to the output memory SP(G), whereas during ongoing operation the average value to which a safety factor Res has been applied is present as a static limit value G stat .
  • maximum curve shapes of the load current can also be stored and used for forming limit values instead of the maximum measured current values. Consequently, each time a current limit value is exceeded the time characteristic curve is also compared with earlier time characteristic curves of overcurrents. In this way, the control unit 1 learns current consumption patterns that are typical for the system, with a tripping of the protective device being induced only if the current consumption patterns are hugely exceeded.

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US13/058,731 2008-08-13 2009-06-05 Electric system Active 2031-01-15 US8842403B2 (en)

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US9819510B2 (en) * 2012-11-20 2017-11-14 Thales Power over data transmission
US10483748B2 (en) 2015-04-09 2019-11-19 Harting Electric Gmbh & Co., Kg Junction box and network for distributing energy
US20170179835A1 (en) * 2015-12-22 2017-06-22 Siemens Aktiengesellschaft Clocked power supply with low-voltage output
US10587198B2 (en) * 2015-12-22 2020-03-10 Siemens Aktiengesellschaft Clocked power supply with low-voltage output
US10777997B2 (en) 2017-02-09 2020-09-15 Ellenberger & Poensgen Gmbh Method for operating an electronic circuit breaker, and electronic circuit breaker
US12443150B2 (en) 2020-06-11 2025-10-14 Chemelex Europe Gmbh Systems and methods for controlling digital circuit breakers

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RU2504881C2 (ru) 2014-01-20
AT506092B1 (de) 2009-06-15
AT506092A4 (de) 2009-06-15
US20110141643A1 (en) 2011-06-16
RU2011109200A (ru) 2012-09-20
EP2313952A1 (de) 2011-04-27
CN102124619A (zh) 2011-07-13
EP2313952B1 (de) 2018-03-21
WO2010018018A1 (de) 2010-02-18

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